Research - The broad objective of the proposed study is to identify the coordinated muscle actions used by the postural control system to maintain upright stature and to investigate the effects of age on these actions. These studies will lead to a better understanding of the changes that occur in the postural control system due to age. The long-term goal of studying postural balance in the elderly is to reduce injuries due to falling. In order to assess the coordination of muscle actions, a method to estimate individual muscle forces exerted by the major muscles acting on the ankle will be developed and validated. Based upon previous studies by the Principal Investigator (Redfern, 1988). Characterization of postural control strategies (i.e. coordinated muscle actions to maintain balance) of both elderly and young adults will be performed using this force estimation procedure.